1. Field of the Invention
This invention relates to a process for preparing organic halides and in particular to a process for selectively substituting an hydroxyl group with a halogen.
2. Related Information
Alcohols are a very common starting point in organic synthesis, and a common reaction in such an organic synthesis is the conversion of the alcohol into an organic halide. This conversion has usually been effected by the use of hydrogen halides and/or certain phosphorus trihalides.
Various other methods are known for preparing the versatile organic halide intermediate, e.g., the Sandmeyer reaction wherein an aromatic nitro group is reduced to an amine, diazotized, then reacted with copper chloride to yield the corresponding chloroaromatic compound.
The use of aryl phosphorushalides of formula: R.sub.n PX.sub.5-n wherein n is selected from 1, 2 and 3; R is selected from the group consisting of C-6 to C-10 aryl and substituted aryl wherein the substituents are selected from the group consisting of: straight and branched chain alkyl, alkoxy, and haloalkyl; halogen, sulfonate and mixtures thereof; and X is a halogen, and particularly the use of phenylphosphorustetrachloride (PPTC), as a reagent for organic synthesis is practically unknown. Timokhin, B. V.; Dmitriev, V. K., Dmitriev, V. I., Zh. Obshch. Khim 1984, 54, 1290, reported the reaction of cyclohexene with PPTC to give trans-1,2-dichlorocyclohexane and 3-chlorocyclohexene. Mitrasov, Y. N.; Vladyko, E. D.; Kormachev, V. V. USSR SU Nos. 1,051,097 and 1,051,096 found that treatment of aliphatic aldehydes and ketones with PPTC produced geminal dichlorides. PPTC has also been used to produce tetrazines from hydrazines, see Yagupol'skii, L. M.; Matyushecheva, G. I.; Mikhailov, V. S.; Bulygina, L. A. USSR SU No. 498,300 and Matyushecheva, G. I.; Mikhailov, V. S. Yagupol'skii, L. M., Zh. Org. Khim, 1974, 10, 124.